Mixed Disilyl-Substituted Cyclopentadiene Derivatives and Corresponding Zirconium, Molybdenum and Tungsten Compounds

The mixed disilyl-substituted cyclopentadiene C 5 H 4 [Si-Me 2 (CH=CHCH 3 )](SiMe 3 ) (2) has been synthesized in a one-pot reaction by alkylation, deprotonation and silylation of C 5 H 5 (SiMe 2 Cl). The analogous olefin-tethered cyclopentadiene C 5 H 4 [SiMe 2 (CH 2 CH=CH 2 )](SiMe 3 ) (3) has been obtained through traditional metathesis routes from Li[C 5 H 4 -(SiMe 3 )] and the chloroallylsilane SiMe 2 (CH 2 CH=CH 2 )Cl. The corresponding mixed disilyl-substituted cyclopentadienyllithium salts Li[C 5 H 3 -SiMe 2 R-3-SiMe 3 ] [R = CH=CHCH 3 (cis+trans-4); R = CH 2 CH=CH 2 (5)] were used to isolate the chiral zirconium compounds [ZrX(η 5 -C 5 H 4 SiMe 2- η 1 -NtBu)-(η 5 -C 5 H 3 -1-SiMe 2 R-3-SiMe 3 )] [X = Cl, R = CH=CHCH 3 (cis+trans-6); R = CH 2 CH=CH 2 (7); X = CH 3 , R = CH=CHCH 3 (cis+trans-8); R = CH 2 CH=CH 2 (9)] and group 6 derivatives [MH(η 5 -C 2 H 3 -1-SiMe 2 R-3-SiMe 3 )(CO) 3 ] [R = CH=CHCH 3 , M = Mo (cis+trans-10), M = W (cis+trans-11); R = CH 2 CH=CH 2 , M = Mo (12) and M = W (13)], which have been fully characterized. The behaviour of metal compounds 8-13 has been studied and compared with that previously reported for monosubstituted alkene-silylcyclopentadienyl systems [Zr(CH 3 )-(η 5 -C 5 H 4 SiMe 2 -η 1 -NtBu)[(η 5 -C 5 H 4 SiMe 2 )(CH 2 CH=CH 2 )] and [MH(η 5 -C 5 H 4 SiMe 2 -η 1 -NtBu) [(η 5 -C 5 H 4 SiMe 2 )(CH 2 CH=CH 2 )] (M = Mo, W).